Conventionally, communication system designs typically use point of load power line filtering due to numerous reliability issues associated with filtering at a Power Distribution Unit (PDU). Alternatively, conventional system designs can use redundant PDU filtering, however this takes up significant space on a module and/or at a rack level which in turn limits space, bandwidth, etc. and increases cost. Conventional systems that use feed power filtering at the rack distribution point must be design and installed as redundant which disadvantageously takes up considerable rack space.
A PDU is a device configured to distribute electrical power. Communication systems are typically deployed in frames or racks with one or more PDUs. The PDUs are connected to an external power supply unit. For example, PDUs can include two 70 Amp modules with dual feeds on each module, two 500 Amp modules with eight feeds to each, an 80 Amp PDU with dual feed, and the like. Currently communications equipment receive power from a Central Office (CO) that is delivered to a fuse (or circuit breaker) panels that is connected to shelves of equipment located in the same rack.
Traditionally, the electromagnetic interference (EMI) generated by other racks of equipment at the CO or other shelves in the same rack requires numerous broadband filters located on each module and fan assembly in the shelf. These filters must be effective at frequencies below 200 Hz to over 200 MHz for reliable operation as well as regulatory compliance. At the lower frequencies, components are large and take up valuable board space as well as generate heat which needs to be removed. At higher frequencies, capacitors need to be connected to a low impedance ground path while meeting 1000V standoff requirements.
Typically, communication systems are deployed through shelves housed on a rack. The rack also includes the PDU which is configured to provide power to the shelves. The shelves are configured to house modules for data processing, input/output interfaces, control, and the like. In the case of a next-generation dense wave division multiplexed (DWDM) system, for example, with three shelves in a rack containing more than sixty data processing modules and up to forty high flow fans modules per rack requires over a hundred filter circuits on the associated modules. The advantage of the traditional method of putting the filter networks on the modules is that the modules are cooled using redundant fans to meet reliability requirements. There are numerous disadvantages in placing that many filter circuits on modules including taking up considerable space limiting the number of data channels in a rack.
Additionally, the shelves utilize individual blank modules with faceplates for unequipped modules. These faceplates can include many features of installed (i.e., equipped) modules including EMI gaskets on two edges and ejector shields. The blanks have a vertical member to direct air-flow and simulate the module printed circuit board (PCB). Where multiple slots depending on system configuration need covering, a larger blank with single vertical section have been used as well as multiple single slot blanks.
The use of individual blanks with a single vertical member and gaskets on vertical edges has limitations such as requiring multiple blanks where several slots need covering and the air-flow in the blank area is greater than across adjacent module heat sinks and components because the pressure is much lower where the blanks are installed. The present single slot blank also has cost and environmental performance issues. The use of multiple slot blanks with a single vertical member and gaskets on vertical edges has even greater air-flow in the blank area than across adjacent modules with heat sinks and components because the pressure is much lower where the blank are installed. The single slot blank all has EMC issues due to structural weakness and environmental performance issues due to the lower pressure. The result is significant flow bypass in the air around the blank which starves the active modules that require more airflow.